The light from headlights at night (or in bad weather) will always cause some level of glare for most drivers. Glare reduces a driver’s visibility and increases the risk of an accident, especially on two lane highways.
For your DMV test, you should be aware of the risks and know what to do when you are exposed to headlight glare.
Your Visibility is Affected
If an oncoming driver doesn’t dim the vehicle’s headlights at night, glare will most likely affect your visibility.
It affects you, not only while the light is visible, but also after the glare is no longer in your field of view. Why is this? Well, after the vehicle has passed by, it takes some time for the pupil to readjust to the less intense light.
Older drivers, impaired drivers, and drivers in poor physical condition usually find glare more difficult to handle since it takes longer for their eyes to recover.
The brighter the headlights, the greater the glare is, the less you can see of the road ahead and the longer it will take for your eyes to recover.
Common Questions about Dimming Your Headlights
State laws vary.
A rule of thumb is to dim lights when you are within 500 feet of oncoming traffic. This is also the law in most states.
Iowa, Michigan, Minnesota, Montana, and Oklahoma require dimmed lights when within 1,000 feet.
New Hampshire when within 150 feet.
Some states leave it up to your judgment (no specified distance).
NHTSA recommends 300 feet, but state rules vary.
Hawaii, Kansas, Mississippi, New Jersey, North Carolina, Ohio, South Dakota, and Vermont don't specify any distance.
Oklahoma law requires you to dim your lights when you are following within 600 feet.
In Montana, Tennessee, and Wisconsin the distance is 500 feet.
Iowa: 400 feet.
Oregon: 350 feet.
Alaska, California, Connecticut, District of Columbia, Florida, Illinois, Maine, Maryland, Missouri, Nevada, North Dakota, Pennsylvania, Texas, Utah, Washington, and Wyoming: 300 feet.
Alabama, Arizona, Arkansas, Colorado, Delaware, Georgia, Idaho, Indiana, Kentucky, Louisiana, Massachusetts, Michigan, Minnesota, Nebraska, New Mexico, New York, Rhode Island, South Carolina, Virginia, and West Virginia: 200 feet.
New Hampshire: 150 feet.
In everyday driving, this is usually a non-issue. High beams let you see about 350-500 feet ahead. When you can see the car ahead with your high beams, you are at risk blinding the other driver. That's when you should dim your lights.
Drifting in Your Lane
When you are exposed to oncoming headlights and experience the negative effects of glare, you tend to drift from your lane. On a two-lane highway (one lane of traffic opposes another lane of traffic), you may drift closer to the right edge or to opposing traffic. If you drift to the side of the road, you may be in danger of hitting pedestrians walking on the shoulder or side of the road. Or you may run off the road.
If you drift to the center, you may collide with an oncoming vehicle.
Glare from Oncoming Vehicles
Question 1: To avoid glare from high-beam headlights of an oncoming car, you should:
- A. Focus on the center line on the road.
- B. Look to the lower right side of your lane.
- C. Keep your own headlights on high beam.
CORRECT ANSWER: B.
When you see less of the road ahead, you must slow down. To reduce the effects of glare from oncoming headlights, look to the lower right side of your lane.
Don’t look directly at the headlights of oncoming traffic.
Instead, shift your eyes and look down to the right side of your lane. Use the right side for tracking your lane rather than the left side. You will still be able to see other vehicles with your peripheral vision.
If other drivers don’t dim their headlights, don’t try to “get back” by switching on your own high beams. Briefly flashing your headlights can tell the other driver that he or she is driving with their bright lights on. But be aware that the legality of headlight flashing varies by state.
In Florida, as an example, headlight flashing is protected by free speech pursuant to the First Amendment.
In North Dakota and Michigan, as other examples, it is illegal to flash high beams within 500 feet of oncoming traffic.
If you keep your headlights on high beam, both of you may be blinded.
Glare from Behind
Today, most rear-view mirrors have a night setting. By using a small lever at the bottom of your mirror, you will dim bright lights appearing in the mirror. You will still see vehicles that approaches from behind, but their headlights will create much less glare and probably not bother you.
If glare is caused by your side mirrors, make sure they are properly adjusted. By leaning a bit to your left, you should see no more than the left rear corner of your vehicle. Same thing when you lean to your right. Adjust your passenger side mirror until the right rear corner is just visible.
Glare from Your Own Headlights
Sometimes, your own headlights can reflect and cause glare. This often happens when you drive with your high beam headlights in fog, mist, heavy rain or snowfall. When the light from your headlights reflect off the moisture in the air, the effect is blinding rather than illuminating.
By switching to low beams, you can reduce this blinding effect.
The following are examples of DMV questions about headlights settings in bad weather:
Question 2: When driving in fog, you should turn on:
- A. Low beam headlights
- B. Parking lights
- C. High beam headlights
CORRECT ANSWER: A.
Use your low beam headlights in fog.
Question 3: When driving in foggy conditions, high beams will:
- A. Reduce glare
- B. Improve your ability to see ahead
- C. Cause glare
CORRECT ANSWER: C.
In foggy conditions, high beams can reflect and cause glare.
Learn more about Driving in Fog for your DMV test.
The Importance of a Clean Windshield
A scratched and dirty windshield makes glare worse.
Always keep the inside and outside of your windows and windshield clean. Having a clear view while driving is important, especially in bad weather.
A clean windshield also helps your wipers to work smoothly. A dirty or scratched windshield makes your windshield wipers less effective.
If you come across small cracks on your windshield, you should have them fixed as quickly as possible.
In winter, always remove snow and ice off your windshield, mirrors, headlights, and taillights. And don’t forget the roof!
Clean the Car’s Headlights
Clean and properly aligned headlights will help you see and be seen. Even small amounts of dirt on the headlamps can severely reduce the light output.
Properly aimed headlights are also important for reducing the risk of casting glare on other drivers.
Want to Learn More?
Do you want more questions about use of headlights and night driving? Go here: DMV Questions about Night Driving.